Direct keyboard transmitter



March 3, 1942. J SPENCER 2,274,911

DIRECT KEYBOARD TRANSMITTER Filed May 51, 1941 2 Sheets-Sheet l INVENTORATTORNEY March 3, 1942. J. A. SPENCER DIRECT KEYBOARD TRANSMITTER 2Sheets-Sheet 2 Filed May 31, 1941 INVENTOR W ATTORNEY Patented Mar. 3,1942 DIRECT KEYBOARD TRANSMITTER James A. Spencer, Teaneck, N. .L,assignor to Radio Corporation of America, a corporation of DelawareApplication May 31, 1941, Serial No. 395,911

Claims.

This invention relates to keyboard transmitters for telegraph systemsand more particularly to a transmitter of the type which is adapted totransmit synchronized signals.

In ordinary start-stop keyboard transmitters no continuoussynchronization is required between the transmitting and receivingstations since the cyclic transmission of each .code signal as initiatedat the transmitter is closely enough followed by the speed of operationof the receiving instrumentality. The keyboard transmitter whichconstitutes the subject matter of the instant invention, however, is onewhich transmits the code signals for each character in a predeterminedtime relation to the operation of a time division simplex or multiplexdistributor. Such a distributor may be run continuously and a receivingdistributor can be maintained in synchronism wtih the transmittingdistributor by well known means.

The preferred embodiment of my invention as herein shown and describedis adapted for operation in conjunction with a signalling code composedof combinations of marking and spacing impulses the number of which isuniform for each character. As illustrated, the arrangement transmitscode signals of the 7-unit type, al though the invention itself may beadapted for use with code signals of five or more units.

The principal object of my invention is to provide a direct keyboardtransmitter suitable for operation in conjunction with synchronouslydriven distributors. It is a further object, however, to provide asuitable means for mechanically starting code selections without undulylimiting the keyboard action.

Still another object of my invention is to provide a keyboard-actuatedcode signalling system which operates by depression of a key to firststore the elements of a code signal, then to actuate a keying device inproperly timed relation to the operation of a synchronously drivendistrib-' utor.

Other objects and advantages of my invention will be made clear in thedescription to follow.

In describing my invention reference will be made to the accompanyingdrawings, in which Figure 1 shows an elevation view of the componentparts of a keyboard transmitter essential to the carrying out of theinvention;

Fig. 2 shows a plan view of a portion of the same keyboard transmitter;and

Fig. 3 is a fragmentary view of certain structure which includes amagnetically operated pawl, disengagedfrom its cam.

For the sake of simplicity in describing the mechanical structure of apreferred embodiment, the complete assembly of parts to be found in atypical keyboard instrument has been shown in the drawings in a more orless schematic manner.

The key levers I5 are shown in cross-section in Fig. l and in plan viewin Fig. 2. These levers are pivotally mounted inside a hollow base 22,the pivot rod common to all of the key levers being positioned in therear of the base, but not shown in the drawings.

Underlying the key levers are seven code bars [6 and an actuating barl3. The code bars l6- are selectively and longitudinally shifted inresponse to the depression of any key and different code bars areselected for actuation in accordance with the saw-tooth configuration ofeach one thereof in relation to the opposing key levers l5. Each keylever, therefore, selects one or more code bars IS in accordance withthe marking elements of the code signal to be transmitted. The movementof the selected code bars is in the direction of the arrow, that is, tothe right as viewed from the front of the machine (Fig. 1).

The downward movement of the key levers 15 also depresses an actuatingbar l3 which is mechanically connected to a vertical link rod H. Theupper portion of the rod ll extends through an eyelet in the horizontalarm of an elbowleverlZ and carries two nuts 40, one of which bears onsaid arm and pulls it downwardly when any key is depressed. The elbowlever I2 is pivoted at 45. e

The upstanding arm of the elbow lever i2 is arranged to withdraw a pawlI0 from engagement with a cam, member 2|. Mounted on the same shaft with.the cam 2| are other cams which cooperate with different parts of themechanism presently to be described. The entire assembly of the cams isurged in a counterclockwise direction by means of a spring 8 attached topins 3 and 8.

The cam assembly 26 is journaled in the frame 25, the latter beingfastened to the base 22.

Each of the code bars I6 is associated with a lever l4 pivoted onbearing 29. The lever I4 has linked thereto a horizontal lever l8, theleft end of which is suitably held in position by means of a comb l1.

The left ends of the levers i8 are provided with an upstandingprojection 3| which is so positioned beneath the right and leftshoulders 32,

and 3d of associated levers l9 as to permit of setting the lattermembers suitably for transmitting the necessary code elements of thesignals. Thus, when a key is depressed, if the number i element of thecode signal is to be a mark ing element, then a saw-tooth in code bar I6for number position in the cod seign-al will be disposed underneath theselecting key bar [5. Shifting of a code bar iii to the right will drawlever E8 to the left. In the shifted position projection 3! will comeopposite the shoulder 32 on the lever l9. Almost simultaneously theactuating bar IE will cause the connecting link H to be drawn down forreleasing the pawl In so that spring 6 will turn the cam assembly 26-suffi ciently to permit the cam member 2| to release a group ofhorizontal levers [8 for actuation by the springs 5. Those of the leversl8 which have been drawn to the left will actuate the levers IE to tiltthem in a clockwise direction on the pivot 27. Those of the levers 18which have not been drawn to the left will, when lifted by the springs5, engage the upstanding projection 3! with the right hand shoulders Monthe levers l9 and so tilt them in a counter-clockwise direction.

Each of the levers l9 constitutes amounting for a contact spring 'Iwhich is movable between two stationary contacts M and S. The stationanycontacts M are preferably connected to the positive terminal of a directcurrent source, while the stationary contacts S are likewise connectedto the negative terminal of such asouroe. The contacts T are connectedrespectively to different code segments l to l inclusive of thesignalling distributor ring Rl. These code segments are bridged across acollector ring 35 by brush 36. The ring 35 may be connected toa'suitable keying device for a radio transmitter. The keying device maybe adapted for simplex or multiplex transmission of synchronizedsignals.

The code bars it have slanting walled notches beneath the key bars whichare to move them to a marking selection. J

Any code bar It which is not to'be shifted by a key bar 85 (because thecode element is to be a space) must have a square notch 4| beneath thekey bar under consideration. The depression of the key bar into a squarenotch will'simply lock that code bar in place for the purpose ofpermitting the transmission of a space signal.

The sequence of steps necessary to set the cohtacts T against theirspacing contacts S or marking contacts M is initiated by theenergization of magnet I when the brush 3i sweeps over contact segment 5in ring R2 for bridging the same across the collector ring 38, thelatter being connected to one terminal of a local direct current source.The other terminal of this source is grounded.

Prior to the energization of magnet I, its armature 4 carrying adownwardly projecting bar 4a exerts sufiicient pressure upon a series ofdetents 2 mounted on springs to prevent the movement of the contactspring carriers l9. Hence, even though a key bar I5 is depressed at acertain instant, its effect will not be transmitted to the contacts Tuntil after the next energiz'ation of the magnet I. Those of thecontacts T which are to be moved to the marking position'will be shiftedby the engagement of the project-ion 3| on the horizontal member l8against the shoulder 32 on lever 19. Each lever I9 is connected by anindividual spring 33 to a cross-bar 41) mounted transversely of thearmature lever 4. These springs 33 are placed under tension only whenthe armature 4 is pulled up. They are weaker than the springs 5 so as tobe stretched slightly when a horizontal bar it is pulled up by itsspring 5 for. the purpose of shifting the contact -T to its markingcontact. If the horizontal bar tact T will be shifted for the codesignal element under consideration to the spacing contact S, providedit'was previously held against the marking contact in accordance withthe code element of a previous signal.

Repeated energizations of the magnet l in the absence of key depressionsenable the springs 33 to be utilized for restoring contacts T to thespacing contacts S so that any given code signal which has been set upby a key bar will not be repeated.

It will be seen from the above description that mechanism is providedwhich performs a storage function during the time necessary to transferthe efiects of key depression by the selective setting of code bars 16and until the release of the levers [9 when pressure upon the deterits 2is relieved. This relief takes place upon energization of the magnet land the lifting of its armature 4. The setting of the levers I9 at thatmoment is held until the next energization of magnet I.

During the pull-up and release of the armature 4 the brushes travel oversegments 5, 6 and 7. It is necessary, therefore, to store the eifects ofmarking and spacing code element selections for the 5th, 6th and 7thpositions 'to be utilized in the complete transmission of the signalssubsequently. This storage is effected by electromagnetic means as shownin my copending application Serial No. 357,109, filed September 1'7,1940. Reference is here made to Fig. l of that application for showinghow a part of the code signal may be stored and subsequently utilized.Such a storage device is herein shown as unit M.

Another'function performed by the energization of magnet I is to restoreto normal the cam assembly 26. This operation is performed by causingthe shoulder lfia on pawl It to first slip over the upper end of the camprojection 2| when armature 4 is lifted. Then, upon de-energization ofmagnet I, the pawl Hi presses down- 7 wardly on the projection 2i, beingurged toward the pivot center of the cam assembly 25 by means of aspring 43. The cam assembly 26 then rotates clockwise against thetension of spring 8 and is thereafter locked in normal position untilagain released by either a lateral or a vertical withdrawal of the pawlIE1. With this restoring movement a projection 30 rides under a roller 9on the end of the locking lever 24 so as to free the levers M forrestoration to their normal positions in-case they have been previouslyset to transmit the marking elements of a signal. The projections 39 atthe top of each lever are those which enable these levers to be lockedinone position or the other when the locking lever 26 is lowered alongthe right slope of cam projection 30. Thus, when cam shaft 26 has beenreleased by pawl lB'and tilted counterclockwise, then the roller 9 dropsdown on the right hand face of the projection 30.

The utilization of the code signals as initiated by the passage of thebrush 35 over the segments I to I inclusive in distributor ring RI formsno part of the instant invention, but it may be well understood by thoseskilled in the art. However, a preferred method of keying is that whichis disclosed in the aforesaid copending application.

Summarizing the operation of my keyboard transmitter as above described,it will be noted that, when a key lever I is depressed, certain of codebars I6 move to the right. Levers I4 then rotate about pivot 29. LeversI8, which are pivoted to the upper end of levers I4, are movedhorizontally so that their projections 3| are in such position that,when the springs 5 are allowed to contact, the left hand shoulders 32 oflevers I9 will be lifted. Lever I2 operates near the end of the travelof key lever I5 and releases pawl I0. Cam assembly 26 then rotates inthe direction of the arrow until arrested by stop 8. Levers I8 are thenfreed to move upward under the influence of springs 5. Locking bar 24holds levers I4 to their selected positions until cam assembly 26 isreturned to its original position through the operation of armature 4.As the brush 3! contacts segment 5 of distributor rings R2, magnet I ismomentarily energized. As armature 4 is attracted to the magnet, detent20 is freed and lever I9 is permitted to rotate about its bearing 21 dueto the force exerted by spring 5. The tension on spring 5 will overcomethat on spring 33 if they happen to be opposed. When the armature 4 issubsequently released pawl I0 rotates cam 26 in a clockwise direction,thus restoring the levers I8 to their lowered positions under tension ofthe springs 5.

The locking lever 24 is now caused to free the levers I4 so that theycan be drawn back to normal position by their springs 42. This lastoperation restores the code bars I6 to their normal positions, thuspreparing the same for a subsequent key selection.

Although my invention has been described with respect to a specificembodiment thereof, it will be understood by those skilled in the artthat modifications of the structure may be made without departing fromthe spirit and scope of the invention itself. The invention is,therefore, of such scope as is permitted by the claims.

I claim:

1. In a keyboard transmitter, a group of codeelement contactors settableto marking and spacing positions in accordance with the units of a codesignal, a key-lever-and-code-barassembly having mechanism linkedtherewith for selecting the appropriate position of each of saidoontactors, a cam assembly operable in response to a key depression andarranged to release said selecting mechanism from a normally lockeddownposition, spring actuated means for setting all of said contactorssimultaneously after release of said mechanism, and electro-magneticmeans cyclically operative for causing said release and for subsequentlyrestoring said selecting mechanism to its normally locked-down positionafter each key depression.

2. The combination according to claim 1 and including means undercontrol of said cam assembly for locking up the keys of the keyboarduntil the code combination corresponding to a depressed key has beenstored for subsequent transmission.

3. In :a keyboard transmitter, a group of keyactuated code selectorbars, each bar being. individual to one of the elements of a codecombination, storage mechanism under mechanical control ofsaid codeselector bars, a cam assembly operative in response to the depression ofa character key for causing the set-up of said code selector bars to betransferred to said storage mechanism, a group of keying contactssettable by the storage mechanism against marking or spacing stops, acyclically operative distributor for collecting impulses successively inaccordance with the setting of said keying contacts, andelectro-magnetic means operative at a predetermined moment of thedistributor cycle for terminating the period of storage of each codecombination.

4. The combination according to claim 3 and including locking meansoperative during the period of storage of each code combination wherebysaid code selector bars are locked in their selected positions, thuspreventing the playing of a second key of the keyboard during eachstorage period.

5. The combination according to claim 3 and including a pawl pivoted onan armature of said electro-magnetic means, said pawl being engageablewith an abutment on said cam assembly upon energization of theelectro-magnetic means, said pawl being efiective to restore to normalposition said cam assembly upon deenergization of said electro-magneticmeans, trigger means under control of any selected key in the keyboardfor disengaging said pawl from said abutment on the cam assembly, andresilient means for rotating said cam assembly when released by saidpawl.

6. In a code signal keyer of the start-stop type, a keyboard havingcharacter keys, code bars selectable by the keys, a toggle lever andtilting means therefor individual to each code bar, each toggle leverbearing a contact which coacts with two stationary contacts for settingup a marking or spacing selection of a code element, an actuating baleeffective upon depression of any key to prepare said tilting means foroperation, a locking detent for each toggle lever, electro-magneticmeans cyclically operative to release said detents, thereby to permitthe operation of said tilting means in accordance with the selectivesetting of said code bars, and means operative upon de-energization ofsaid electromagnetic means for resetting said tilting means and saidcode bars.

7. A device according to claim 6 and including a cam assembly whichcarries a cam member engageable with units of said tilting meansindividual to each toggle lever, said cam member being efiective in anon-operated position to restrain the tilting means from operation, and

' upon release of the cam assembly by said actuating bale said member iscaused to free the tilting means for subsequent setting of the togglelevers when the latter are released by their detents.

8. A device according to claim 6 and including a synchronously operabletransmitting distributor having segments appropriate to each codeelementof a uniform length character signal, and connections from each of thecontacts carried by the toggle levers to respective ones of saidsegments.

9. In a code signal keyer of the start-stop type, a continuously drivendistributor having segments for each element of a uniform lengthcharacter signal, a set of movable contacts individually connected tosaid segments, stationary contacts opposing said movable contacts andfed wim signaling; potentials, a. key, board having character: keysand;code:bars-selectively actuated thereby; means 'for settingsaidzmovable contactsineccordance' withzthe code her selection madeby'any'cne of the keys, and means operative to release: said; contactsetting means. for operationionlizat: antinstant' corresponding. to". apredetermined. phase; ofrthe. distributors' operating cycle 10. A:device according to claim 9' and having?

